US20020056759A1

US20020056759A1 - Bar code symbology for consumer scanning applications

Info

Publication number: US20020056759A1
Application number: US09/953,782
Authority: US
Inventors: Frederick Schuessler
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-10-03
Filing date: 2001-09-17
Publication date: 2002-05-16
Also published as: US6761314B2

Abstract

A bar code symbology derived from form a set of patterns of bar and spaces in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space is limited to k modules in width, having a predetermined start pattern; a predetermined stop pattern; and providing the exclusion from the set of valid patterns those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.

Description

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of provisional application Serial No. 60/237,639 filed Oct. 3, 2000.[0001]

COPYRIGHT NOTIFICATION

A portion of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by any one of the patent disclosure, as it appears the Patent and Trademark Office, patent files or records, but otherwise reserves all copyright whatsoever.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to bar code reading and in particular to a new symbol with structure and features that make it particularly suitable for consumer-scanning applications. Its features include a compact start pattern that can be found without compute-intensive ratio checks, and an overall structure that supports variable-length messages while providing strong protection against short reads.

2. Background of the Invention

Bar code symbols are formed from bars or elements typically rectangular in shape with a variety of possible widths. The specific arrangement of elements defines the character represented according to a set of rules and definitions specified by the code or “symbology” used. The relative size of the bars and spaces is determined by the type of coding used as is the actual size of the bars and spaces. The number of characters (represented by the bar code symbol) is referred to as the density of the symbol. To encode the desired sequence of the characters, a collection of element arrangements are concatenated together to form the complete bar code symbol, with each character of the message being represented by its own corresponding group of elements. In some symbologies, a unique “start” and “stop” character is used to indicate when the bar code begins and ends. A number of different bar code symbologies are in widespread use including UPC/EAN, Code 39, Code 128, Codeabar, and Interleaved 2 of 5.

In order to increase the amount of data that can be represented or stored on a given amount of surface area, several more compact bar code symbologies have been developed. One of these code standards, Code 49, exemplifies a “two dimensional” symbol by reducing the vertical height of a one-dimensional symbol, and then stacking distinct rows of such one dimensional symbols, so that information is encoded both vertically as well as horizontally. That is, in Code 49, there are several rows of bar and space patterns, instead of only one row as in a “one dimensional” symbol. The structure of Code 49 is described in U.S. Pat. No. 4,794,239. Another two-dimensional symbology, known as “PDF417”, is described in U.S. Pat. No. 5,304,786.

Still other symbologies have been developed in which the symbol is comprised not of stacked rows, but a matrix array made up of hexagonal, square, polygonal and/or other geometric shapes, lines, or dots. Such symbols are described in, for example, U.S. Pat. Nos. 5,2276,315 and 4,794,239. Such matrix code symbologies may include Vericode, Datacode, and MAXICODE.

Ever since the advent of the Universal Product Code in the 1970's, linear bar code symbols have been widely adopted as an inexpensive but effective way of automating the link between printed numbers on paper and computer databases. Each “symbology” has its own advantages for certain applications. Because bar codes are so common in our daily environment, and used in so many different applications, it is often important that a symbology, or a distinct variant of a symbology, be dedicated to one specific application. For example, a bar code scanning system may read a barcode encoding a string of digits such as “12345678905”. It is very important that the system can unequivocally determine that this string is to be used to look up the price of a grocery item, and that the price can be found, using the decoded string of digits as a key, in a database of numbers assigned by the Uniform Code Council for this purpose. In the past many other symbologies and symbology variants have also been reserved for such specific uses, such as a Code 128 symbol for marking medical instruments, a 14-digit Interleaved Two-of-Five symbol for marking cases for logistics tracking, and a 6-digit Code 39 symbol for marking Telecommunications equipment.

One aspect held in common by all of the above traditional barcode applications, is that a worker (such as a checkout clerk at a supermarket) will be trained and paid to scan the specific kind of barcode required by the application. Recently, however, as the cost of computers, and of scanning hardware, has decreased, a new set of consumer-scanning applications have become feasible.

Consumer-scanning applications will in principle have many requirements in common with traditional bar code applications, except that the consumer-scanning application will increase the difficulty of meeting some of these requirements. In addition, consumer scanning places at least one new requirement on the symbology. The following paragraphs discuss the new requirements, and then the other requirements that differ in degree.

By definition, the consumer scanning system will be used by untrained and unpaid operators. An unpaid operator will simple abandon consumer scanning if it is perceived as difficult or unreliable. An untrained operator will put the scanning system at a disadvantage through poor technique (such as scanning at an angle, or scanning too close to completely cover the bar code). Thus, the ideal consumer-scanning symbology will facilitate easy intuitive scanning, and will survive an untrained operator's mistakes without these turning into decode errors (such as short reads) that could get into the system.

Traditional linear bar code symbologies are “framed” by relatively large areas, to the left and to the right of the bar code, that must be kept clear of all printing. These areas, called “Quiet Zones”, provide technical benefits that make designing and scanning such symbologies easier. However, these Quiet Zones require additional space to be reserved for the barcode. Moreover, they prevent graphics or text from being tightly coupled to the barcode. This is a problem in the consumer scanning environment, where graphical and textual clues, placed immediately adjacent to the bar code, can help untrained consumer operators find the bar code within graphics, and help them understand what the result of scanning a given consumer barcode will be. Thus, the ideal consumer scanning symbology will allow text and graphics to be tightly coupled to the bar code, not kept distant from it.

Many traditional bar code applications need to fit the printed symbols in a relatively small area. Consumer scanning applications increase the importance of this requirement, as the bar codes will need to fit in constrained spaces such as to mark line items in catalogue tables, and to fit within a single line of text in a newspaper article. Thus, the ideal consumer scanning symbology needs to minimize both the height and the length of the printed bar code.

Many traditional bar code applications are cost-sensitive. However, consumer-scanning applications are extremely cost-sensitive. Thus, the ideal consumer scanning symbology can be scanned by a broad range of low-cost scanning technologies, and will be decodable by a low-cost, low-capability microprocessor system.

Most traditional bar code applications suffer from some variation in print quality, often resulting from attempts to save operating costs of label stock and regular printer maintenance. However, extremely poor print quality is usually avoided in business scanning situations, because of the need to maintain a good business relationship between the organization that prints the barcodes, and the organization that must scan them. Consumer-scanning applications are more likely to experience severe print quality problems for two reasons. First, the checks and balances between a supplier and a receiver in a business relationship will not be present in a consumer-scanning application. Second, consumer barcodes will be printed, not on labels, but on newspapers, in yellow pages, and on other forms of paper that are not amenable to high-accuracy printing. Thus, the ideal consumer scanning symbology can tolerate severe printing defects without an increased risk of false reads (mis-decodes).

Unlike with traditional bar code applications, consumer-scanning printing will often be done without benefit of professional expertise. A particular concern is that the traditional white-space requirements to the left and right of the barcode would often be ignored, in an attempt to fit the barcode into the requirements of a classified advertisement or other space-constrained application. Thus, the ideal consumer scanning symbology would be tolerant of text and graphics immediately adjacent to the bar code.

SUMMARY OF THE INVENTION

1. Objects of the Invention

It is a general object of the present invention to provide an improved bar code symbology.

It is another object of the invention to provide a bar code reader capable of reading the improved symbology.

It is a further object of the present invention to provide a printer for printing the improved symbology.

It is a still further object of the present invention to provide software capable of decoding the improved symbology.

It is an even further object of the invention to provide a method which can be used to accomplish one or more of the above objectives.

Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the following detail description, as well as by practice of the invention. While the invention is described below with reference to preferred embodiments, it should be understood that the invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional applications, modifications and embodiments in other fields, which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of significant utility.

It is an object of the present invention to provide a machine-readable symbology, in which consumer-friendly text and graphics may be printed in direct contact with the leftmost and rightmost bars of the symbol, and may even coincide with these leftmost and rightmost bars.

It is still another object of the present invention to provide a variable-length linear symbology that does not require large white spaces at either end of the bar code, and yet resists short-reads without needing to explicitly encode the length of the symbol.

It is an object of the present invention to provide a machine-readable symbology that includes a space-efficient “finder” pattern, that facilitates a rapid search through text and graphics without the need to perform arithmetic upon sums of multiple bars and spaces.

It is a goal of the present invention to provide a machine-readable symbology that includes space-efficient “Start” and “Stop” patterns, that are also unique patterns that cannot be found at any incorrect location within the bar code symbol, even if the symbol contains print defects, or has been scanned at an angle, or at the wrong distance (resulting in an out-of-focus or otherwise distorted signal).

2. Summary of the Invention

The present invention provides a bar code symbology derived from a set of patterns of bar and spaces in which each character spans a distance of m module widths and is represented by n bars and p spaces; and the largest single bar or space is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein the improvement consists of the exclusion from the set of valid patterns those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.

The present invention further provides a information bearing machine-readable carrier including a substrate; and a pattern of bars and spaces on said substrate in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein excluded from the set of valid patterns are those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.

The present invention further provides an imager for obtaining image data of a target in an image field the target including a symbol having a pattern of bars and spaces in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein excluded from the set of valid patterns are those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol; and a decoder for processing the image data to derive the information contained in the symbol.

The novel features and characteristics of the invention are set forth in the appended claims. The invention itself, however, as well as other features and advantages thereof, will be vest understood by reference to a detailed description of a specific embodiment, when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWING

FIG. 1 shows a sample of the preferred embodiment of the disclosed symbology, encoding the digits “1234”. [0034]
FIG. 2 shows an embodiment of the present invention in which the symbology is implemented on a carrier, and read by a scanner or reader; and [0035]
FIG. 3 shows an embodiment of the present invention in which the symbology is printed on a carrier.[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENT

Every linear symbology uses sets of predefined bar/space patterns to encode information. The present invention uses a set of patterns with several characteristics in common to each pattern (called a “symbol character”). Each symbol character of the preferred embodiment consists of 3 bars and 3 interleaved spaces, and spans a total of 11 unit widths (or modules). The largest single bar or space in a pattern is limited to 4 modules in width; and (as a parity check to catch printing or scanning errors), the sum of the three bars of a pattern is always an even number. In the terminology commonly used in the literature, this may therefore be described as an ([0037] 11, 3, 4, E) symbology. Code 128 uses all 108 possible patterns from the set of (11, 3, 4, E) patterns, whereas in the preferred embodiment, the present invention selects just 100 of these patterns to encode data, and three more that may only be used in the check-character position. The remaining (11, 3, 4, E) patterns are excluded in order to guarantee that, in the preferred embodiment, the defined Start pattern at the left end of the symbol, and the defined Stop pattern at the right end of the symbol, cannot also appear at any other point within the symbol.
Most linear symbologies known in the art rely on two large white spaces (called “Quiet Zones” or “Margins”) to delineate the start and stop of the bar code. These spaces are usually about the width of a data character (each nominally 10× wide). Since these large spaces are much larger than the maximum space element allowed for the symbology, they help ensure that a false start or stop pattern within the barcode cannot result in a mis-decode or short read. Thus, for traditional symbologies, it is not important that the Start and Stop patterns be unique at off-boundary locations within the symbol. [0038]
The Appendix sets forth the specification of the symbology according to the preferred embodiment of this invention. It contains a table (Table 1) showing all of the patterns used to encode data according to the preferred embodiment. The specification also contains figures showing the start and stop patterns of the preferred embodiment. T he Appendix adds a specific graphical element at the left end of the bar code (in fact, the graphic overlaps the leftmost bar of the symbol). [0039]
The first step in specifying and defining a symbology in accordance with the present invention is to select a character set with a sufficient number of distinct and reliably-decodable patterns to meet the requirements of the application. In the preferred embodiment, illustrated in FIG. 1, an ([0040] 11, 3, 4, E) symbology was selected as the starting point, because it has a sufficient number of patterns (108) to encode pairs of digits efficiently. In this particular case, only 100 combinations are required to encode all the possible digit pairs. However, a robust check character should be a prime number, and 103 is the smallest prime that is equal to or greater than 100. To minimize the risk that a scanner would confuse the preferred embodiment with the standard Code 128, the present invention does not use the two (11, 3, 4, E) patterns that Code 128 uses for its Stop pattern. To further minimize the same risk, the present invention restricts the use of the three Code 128 Start patterns to appear only in the check character position (where they are adjacent to the present invention's Stop pattern, which is not a valid Code 128 data pattern).
The next step is to determine one or more patterns that can be excluded from appearing within any combinations of data patterns. In the case of the preferred embodiment, a pattern of six successive one-module elements (bar, space, bar, space, bar, space, all of unit width) was the starting point. This pattern can be excluded from appearing within any combination of undamaged ([0041] 11, 3, 4, E) data characters, by eliminating just two of the possible patterns: the pattern starting with four narrow elements, and the pattern ending with four narrow elements. The resulting set of patterns, as used in the preferred embodiment, is shown in Table 1 of the attached specification. In the preferred embodiment, this pattern was extended to eight narrow elements, rather than six, so as to make it much less likely that this pattern would be falsely recognized when scanning other symbologies.
A pattern of all-narrow elements is not the only pattern that can be chosen within the scope of the present invention, but it has several technical advantages. It is, by definition, the smallest pattern for a given number of bars and spaces. Also, it is a pattern that cannot be created spuriously by the scanner, if scanning out of focus. A “blurred” signal can create spurious wide elements, for example by accidentally combining an all-narrow bar/space/bar sequence into one false three-module-wide bar. This phenomenon can be called a “merge” of elements. However, a blurred signal cannot create smaller elements out of larger ones. [0042]
A pattern of all-narrow elements must be long enough to avoid a printing problem, which can have the opposite effect as above: this phenomenon can be called a “split” of elements. A single print defect (a dark spot or a light void) can break up one large element into an apparent sequence of three narrow elements. Enough narrow elements must be defined in the pattern to ensure that, even in the presence of such a print defect, a data character cannot be mistaken for a start or stop pattern. In the preferred embodiment, the sequence of eight narrow elements avoids this problem, because even if a single wide element breaks up into three narrows, no data character or data character sequence contains five narrow elements adjacent to the wider element. It would take two print defects in neighboring wide elements to create a false pattern of all-narrow elements. [0043]
The chosen sequence of eight narrow elements is called the “Finder pattern” of the symbology (as shown in FIG. 1). The next step in the present invention is to add elements to the Finder pattern, if necessary, to ensure that it can be distinguished from other patterns in this and other symbologies, without requiring that sums of elements be compared. The reason for this requirement is so that low-cost microprocessors can efficiently parse a scan of data, and quickly find or eliminate this Finder pattern as a possibility. A low cost microprocessor typically has an 8-bit Arithmetic and Logic Unit (ALU). Individual bars and spaces can easily be measured and stored as single 8-bit quantities (using a sampling rate that supports adequate resolution over the full range of print densities and scanning distances). However, a sum of elements will often exceed the capacity of an 8-bit number, thus requiring 16-bit mathematics, which on an 8-bit processor can be too slow for acceptable performance. [0044]
In the prior art, in particular in the case of Channel Code, a Finder pattern of all-narrow elements has been utilized. However, scanners deal in relative, not absolute, measurements of bar and space widths, because the distance from the barcode (and thus the apparent size of the bars and spaces) is usually not known at the time of scanning. A first step in recognizing the pattern of the preferred embodiment is to examine neighboring individual elements of the same color, to detect a series of four like-sized bars, interleaved with a series of four like-sized spaces. Note that the bars and spaces are checked separately, because system ink spread could easily cause the series of bars to appear significantly larger than the interleaved spaces. However, once two interleaved series of “like” elements are found, the scanner requires some additional means for determining if a series of 8 elements represents 8 one-module elements, or 8 two-module elements. In the case of Channel Code, this was accomplished (to a reasonable degree of certainty) by comparing the total width of the supposed string of narrow elements to the total width of a series of adjacent elements, which should represent the adjacent data character. [0045]
In the present invention, the need for summing elements is avoided. The way this is done, is to define the full Start pattern of the symbology as consisting of the eight narrow elements of the Finder, combined with an adjacent pair of elements (a space and a bar) of predetermined relative widths. This allows the scanner to determine that the “like” elements are indeed single-module elements. In the preferred embodiment, the space is three modules wide and the bar is two modules wide. The purpose of the three-module space is that, in all of the linear symbologies in current usage, individual elements of the bar code are at most four modules wide. Therefore, a 3:1 ratio between two adjacent spaces cannot occur, unless the smaller space really is a 1-module space. In the preferred embodiment, the fixed wider bar is two modules wide, rather than three, so that these two wide elements are of different widths. This difference, between a nominal wide bar and a nominal wide space, never occurs in any of the “binary” codes such as Code 39. Thus, the specification of two different widths for the two “wide” elements next to the finder assures that the Start pattern of the preferred embodiment cannot be found by accident within a binary code. [0046]
A fast 8-bit finding algorithm can perform the basic search while considering only comparisons between adjacent elements of the same color. Without needing to perform any summing operations or other 16-bit math, virtually all false patterns can be quickly rejected, merely by finding four “similar” bar elements, preceded by a bar that is more than 1.5 times bigger than the smaller of the two adjacent bars, with a single interleaved space (next to the “large” bar) that is at least 2 times bigger than the next interleaved space. Then, a further 8 bit check can be made, that all four of the supposedly-narrow spaces are “similar” to each other in width. Only after all of these checks have passed, does it become prudent to perform some 16-bit math (e.g., to verify the expected 8:11 ratio between the Finder and the adjacent data character). One additional step can be executed, if an accurate determination is to be made that the adjacent space and bar are of [0047] widths 3 and 2, respectively, for the purpose of rejecting this pattern within binary codes. This step is to adjust the measured widths for uniform ink spread (because large amounts of ink spread can distort these ratios). The finder pattern, of eight successive equal-sized elements, forms an excellent “ink-spread gauge”. The amount of ink spread can easily be calculated by finding the average bar width and the average space width in this series of equal-sized elements, and then adding or subtracting this average ink-spread number to adjust the widths of the adjacent space and bar before checking the 3:2 ratio.
The next concern addressed by the present invention is the need to define a variable-length symbology that minimizes the possibility of certain class of mis-decode known as a “short read.” A short read can occur in some symbologies, notably Interleaved Two of Five, because the scan line was improperly aligned (and did not cover the entire printed bar code end to end). To prevent this sort of error, a Stop pattern must be selected that cannot be falsely created by a scan line that exits the barcode prematurely. In a symbology without required Quiet Zones, a short read could also occur because a printing defect caused a data character to falsely appear as the Stop pattern. Thus, in a no-Quiet-Zone variable-length symbology, special care must be taken to avoid short reads. In the prior art, a variable-length no-Quiet-Zone symbology known as RSS-Expanded has taken the approach of encoding the length of each symbol within itself (actually, encoding it redundantly using two different mechanisms to avoid a single decode error causing a short read). However, this approach significantly increases the size of the bar code. The present invention aims to prevent short reads via careful selection of a Stop pattern. [0048]
In traditional linear symbologies, which define large required white-space areas (“Quiet Zones”) at both the left and right ends of the bar code, the rules for these Start and Stop patterns have been less strict. It has been sufficient to define start and stop patterns that are only unique on a character boundary, but that are not unique off-boundary. This has worked because these large white spaces “frame” the bar code within the scan line; should a print defect or blurred scanner signal caused too many or too few elements (due to a split or a merge) to appear between the quiet zones, this is easily detected, and the scan can be rejected. However, it is an aim of the present invention to work reliably without a requirement for the added print area of quiet zones. This requires that the Stop pattern be unique, both on-boundary and off-boundary (to withstand the effects of splits and merges), and also requires that a single printing defect cannot transform a data character into a Stop pattern, again whether on- or off-boundary. [0049]
In the preferred embodiment, a pattern similar to, but distinguishable from, the Finder pattern was chosen: the 8-element sequence ([0050] 1, 1, 1, 1, 2, 1, 1, 1) starting with a 1-module bar, and ending in a 1-module space (which is terminated by a bar of any width). When decoding a correctly printed and scanned symbol, this pattern is easily distinguished from the (11, 3) data characters, because it only contains 7 modules, rather than 11, in its first six elements. Unlike a standard Code 128 Stop pattern, this Stop pattern cannot even appear off-boundary (if a printing or scanning defect cause splits and/or merges, creating a wrong number of elements along the way). It can be seen by inspection that this pattern cannot be falsely created if off by two bars from the correct character boundary, because this could only cause a problem if a data character either began or ended with four narrow elements (but these have been excluded). If off by one bar position, then this pattern could only be created by a data character ending with (1,1) followed by a data character of (1,1,2,11,11). But this pattern, comprising only seven modules in total, is not a defined data character.
Other kinds of scanning and printing errors can also be considered, even in tandem, but will not create a false Stop pattern. For example, an angled scan exiting a data character cannot create this Stop pattern. Even on a scan that has gotten off-boundary via splits and merges, the closest match would be an off-by-one-bar scan that exited at the end of the character that starts with ([0051] 1,1,2,1), but this character ends in (3,1), and so a scan exiting at this point cannot mimic the stop pattern. As a further example: there is a data character with the bar/space pattern (3,1,2,1,1,3). If a print defect splits the first bar into three, the resulting pattern is (1,1,1,1,2,1,1,3), and the last space element is incorrect for a Stop pattern (and cannot be made correct by an angled scan line). Similarly, all of the other possible “splits” of data characters cannot make a false Stop pattern.
A different character set for the data characters could be utilized, so long as the patterns used for data are chosen so as to eliminate matches with the selected start and stop patterns. For example, an ([0052] 11,3) code could be used, but where the selected patterns all are such that the sum of the bars are odd, rather than even. In this case, the Start and Stop patterns of the preferred embodiment could still be used.
A different (n,k) symbology (eg, the ([0053] 4,17) patterns of PDF417), could be used as the starting point.
A different pair of start and stop patterns could be used, so long as the combination of data characters and start/stop patterns chosen still maintain the property that the data characters can not be misconstrued as start or stop patterns, even if scanned at an angle, or even if printing or scanning errors are introduced. [0054]
One skilled in the art can appreciate that many variations on the above symbology design can be made, without departing from the spirit of the current invention. [0055]
In addition to the symbology itself, the present invention is also concerned with implementing it on a carrier, reading and decoding it, printing it, and using its data in a communication network. [0056]
Turing to FIG. 2, the symbology of the present invention may be implemented as a [0057] symbol 101 on a carrier 100. The symbol is read by a reader 200, and the data decoded in a decoder 300. A processor 400 may provide user interfaces and applications, which is then connected to a network interface 500 to transfer the data to a communications network 600 to various destinations 701, 702, 703.
Turing to FIG. 3, the symbology of the present invention may be printed as a [0058] symbol 101 on a carrier 100 by a printer 201. The data is encoded from an encoder 301. The encoder 301 may be connected to a processor 400 which provides user interfaces and applications and is also connected to a network interface 500 to allow the data to be encoded to be received from a communications network 600 and various sources 701, 702, 703 on the network.
Although the present invention has been described with respect to bar codes, and apparatus for reading and reproducing such bar code symbols on media, it is not limited to such embodiments. It is conceivable that the method of the present invention may also find application for use with various matching vision or optical character recognition applications in which information is derived from other types of indicia such as characters or from the surface characteristics of the article being scanned. [0059]
In all the various embodiments, the elements of the scanner may be assembled into a very compact package that allows the scanner to be fabricated as a single printed circuit board or integral module. Such a module can interchangeably be used as the laser scanning element for a variety of different types of data acquisition systems. For example, the module may be alternately used in a hand-held scanner, a table top scanner attached to a flexible arm or mounting extending over the surface of the table or attached to the underside of the table top, or mounted as a subcomponent or subassembly of a more sophisticated data acquisition system. [0060]
The module would advantageously comprise a laser/optics subassembly mounted on a support, a scanning element such as a rotating or reciprocating mirror, and elements such as a rotating or reciprocating mirror, and a photodetector component. Control or data lines associated with such components may be connected to an electrical connector mounted on the edge or external surface of the module to enable the module to be electrically connected to a mating connector associated with other elements of data acquisitions systems. [0061]
An individual module may have specific scanning or decoding characters associated with it, e.g. operability at a certain working distance, or operability with a specific symbology or printing destiny. The characteristics may also be defined through the manual setting of control switches associated with the module. The user may also adapt the data acquisition system to scan different types of articles or the system may be adapted for different applications by interchanging modules on the data acquisition system through the use of the simple electrical connector. [0062]
The following claims are intended to encompass all such uses, implementations, and embodiments. [0063]

Claims

1. A bar code symbology derived from a set of patterns of bar and spaces in which each character spans a distance of m module widths and is represented by n bars and p spaces; and the largest single bar or space is limited to k modules in width, comprising:

a predetermined start pattern;

a predetermined stop pattern;

wherein the improvement consists of the exclusion from the set of valid patterns those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.

2. A symbology as defined in claim 1, wherein n is equal top.

3. A symbology as defined in claim 2, wherein the largest single bar or space pattern is limited to four modules in width.

4. A symbology as defined in claim 3, wherein n is equal to three, and each character spans a distance of 11 modules.

5. A symbology as defined in claim 4, wherein the symbology excludes from valid patterns the two patterns that Code 128 uses as a “STOP” pattern.

6. A symbology as defined in claim 5, wherein the three code 128 “START” patterns are excluded from the set of valid patterns except for check characters adjacent said predetermined stop pattern.

7. A information bearing machine-readable carrier comprising:

a substrate; and

a pattern of bars and spaces on said substrate in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein excluded from the set of valid patterns are those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.

8. An apparatus comprising:

an imager for obtaining image data of a target in an image field the target including a symbol having a pattern of bars and spaces in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein excluded from the set of valid patterns are those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol; and

decoding means for processing the image data to derive the information contained in the symbol.

9. An apparatus for generating a signal representative of information encoded in a machine-readable symbol, the symbol including a single row of encoded characters, each character representing an item of data and being selected from a set of detectable mark/space patterns, each said character each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein excluded from the set of valid patterns are those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol, the apparatus comprising:

a) scanning means for scanning the characters within the symbol;

b) means for detecting at least a portion of the reflected light from the symbol and generating an electrical signal indicative of the detected light intensity; and

c) means for decoding the electrical signal to obtain a plurality of corresponding data values representative of said the information contained in the symbol.

10. An article comprising a computer-readable medium that stores computer-executable instructions for decoding a bar code symbology, comprising:

acquiring data from a scan of a bar code symbol; and

decoding the scanned characters according to a symbology definition that excludes from the set of valid patterns those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.

11. An apparatus comprising:

means for producing a representation of a symbol formed from a pattern of bars and spaces in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; and of the exclusion from the set of valid patterns those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol; and

means for printing the representation on a substrate.

12. An article comprising a computer-readable medium that stores computer-executable instructions for encoding a bar code symbology, comprising:

an encoding the scanned characters according to a symbology definition that excludes from the set of valid patterns those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol.

13. An apparatus comprising:

a scanner for obtaining a scan of a target, the target including a symbol having a pattern of bars and spaces in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; wherein exclused from the set of valid patterns are those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol; and a decoding means for processing the scanned sdata to identify information contained in the symbol.

14. An apparatus comprising:

means for producing a symbol image of a symbol formed from a pattern of bars and spaces in which each character spans a distance of m module widths and is represented by n bars and p interleaved spaces; and the largest single bar or space in a character is limited to k modules in width, with a predetermined start pattern; a predetermined stop pattern; and with the exclusion from the set of valid patterns those patterns such that the predetermined start pattern is only at one end of a valid symbol, and the predetermined stop pattern is only at the other end of a valid symbol; and means printing the image on a substrate.